1. Field of the Invention
The present invention concerns a combined opening system for the fins of an unfolding tail unit for projectiles, notably munitions for mortars, provided with a propulsion unit.
2. Description of the Prior Art
For a great variety of reasons, it may be necessary, or at least preferable, to have a tail unit with a span that is greater than the gauge at the rear of a munition. These reasons include a great length of the munition, the optimization of precision, the presence of a propulsion unit to increase the range etc. As a rule, a tail unit of this kind will advantageously be designed to be capable of taking a folded position at rest to make it fit into the gauge in order to reduce the space factor of the munitions and make it easier to handle and stow them. For munitions designed to be launched with a weapon, this ability to be folded becomes a necessity, to enable the munition to be introduced into the gun.
This type of tail unit, commonly called an unfolding tail unit, is formed by a plurality of fins arranged around the munition. Their opening should meet three essential requirements: first of all, it should be triggered after the munition leaves, to preserve the fins against shocks. Secondly, the unfolding should be complete and irreversible because of the major influence of a fin such as this on the trajectory of the munition. Finally, the propulsion unit positioned inside the projectile should be triggered only after the total and irreversible opening of the tail unit. This feature thus forms a safety device for a projectile provided with a propulsion unit.
An object of the present invention is provide for a system for the combined opening of the fins of an unfolding fin which is simple and meets these three requirements in a dependable way.
For a munition designed to be launched with a weapon, advantageously a pressure-sensitive time-delayed igniter will be used. This igniter will be triggered by the pressure inside the gun at the firing instant, the time-delay being greater than the munition ejection time.